'Such views are not welcome in a city like London,' said Ken Livingstone of geneticist James Watson as all his speaking engagements in Britain were cancelled and he returned to a suspension from his institute in the United States. Watson is a nut, and a racist nut at that, but when Ken Livingstone is on a bandwagon I figure it's time to get off.

Watson's views about the intelligence of Africans, let slip absentmindedly in an interview, caused deep offence, yet there was also something self-serving about the people screaming 'racist!' at this elderly loon. Compare Livingstone's reaction with his support of extremist clerics from the Middle East and you begin to yearn for some consistency in his outrage.

The other part of my reservation was expressed by Colin Blakemore, a professor of neuroscience at the University of Oxford, who said: 'Jim Watson is well-known for being provocative and politically incorrect. But it would be a sad world if such a distinguished scientist was silenced because of his more unpalatable views.'

Even when a person's views come from the swamps of a slaver's mind, it is wrong for them to be silenced. Far better to have Watson's pseudo-scientific nonsense out in the open and allow its dispatch by cool reason and moral force.

Livingstone was a Marxist. Sooner or later, every Marxist expresses his sense of public duty by first telling you and me what to say and then what to think. Is it Ken Livingstone's business to define the limits of debate in London? I think not. He may see himself as the person who sets the moral tone for his parish, but he is not ordained by the people to do so, and his readiness to jump into the Watson row lays him open to the accusation that he is using the issue of racism to add lustre to his reputation before next year's election.

We live in a time of official proscription. Every political second-rater is after votes or validation. Justice Minister Jack Straw proposes to add to the laws against incitement to religious hatred by making it a criminal offence to incite hatred against gays, lesbians, bisexuals and transsexuals. This new offence will be punishable by a maximum of seven years in jail. What next? The disabled? Yes, indeed. Mr Straw hopes to protect the disabled with a similar law. After that, there is no telling what this ambitious and calculating man plans. But the attack on free speech must be clear even to the groups which lobbied for this law. When the bill is passed, we will arrive at the absurd situation in which gays who express strong opinions about religious bigotry risk prosecution under one law while religious bigots who express strong opinions about gays risk prosecution under another.

Do we need this? Are our views about each other so violent as to necessitate the intervention of government? And who is to say when a joke or a criticism becomes incitement? If someone claims to feel hatred after a view is expressed, will that be sufficient to put another person away for seven years? Where's the objective proof? Where's the evidence that laws like these change attitudes? In my adult life, there has been a huge change for the better in attitudes about race, gender and sexual orientation. Surely it would be preferable to allow this process to continue without Straw adding to the laws that we already have?

One of the less edifying sights last week was all those academics diving for cover over Watson. Their behaviour reminds us that democracy is for grown-ups. Some discomfort, even pain, comes with the privilege of free speech. We have known that since the Enlightenment, but each generation needs to remember that the downside of free speech is a buffer like Watson trailing a sulphurous whiff of eugenics or the Islamist clerics calling for the death of homosexuals and Jews. The way you deal with them is not with laws, but with savage ridicule.

There are those will argue that the laws Straw promulgates offer us all protection but it is naive to imagine that they will change attitudes. Nothing has prevented Islamist clerics in Britain from breaking every speech crime in the book and this new law on incitement to hatred against homosexuals will not have the slightest impact on them.

In exchange for this meaningless protection, we offer up yet another slice of liberty. A process of infantilisation is underway. It started in 1997 with Straw's Protection from Harassment Act, under which the repetition of an action (i.e. saying something twice) can land you with a conviction, and continued with the opportunistic use of the public order laws and measures against glorifying terrorism and incitement to religious hatred. Are we safer with these laws? No. Less offended? No. Happier as society? No. But we are certainly less free to speak our mind.

But it is not just politicians; columnists and academics are as keen to patrol opinion and escort offenders from the room. The Amis affair is an interesting case. It started with an attack by Marxist critic Terry Eagleton on Martin Amis and his late father, Kingsley, in a new introduction to his book Ideology.The details are by now familiar. Eagleton took Amis to task for the articulation of an aggressive response to Islamist terrorism that dwelt on making the Muslim community suffer with deportation, travel restrictions and strip searching.

The point, ignored by Eagleton and columnist Yasmin Alibhai-Brown, was that Amis prefaced his remarks with: 'There's a definite urge - don't you have it too? - to say...' He was confessing to an urge that millions of people felt after the 7 July attacks or the attempts to blow up a nightclub full of young women in the summer. He was not recommending a campaign of persecution but owning up - bravely, as it turned out - to what amounted to a revenge fantasy. This is what writers are meant to do - to experiment, to give vent to the things so many of us feel but do not express, to allow reason to assert itself and to come out the other end with a view.

Free speech is about the communication of the human experience. Without it, we are diminished: we put our minds in neutral and let others think for us.

While defending himself on Channel 4 News last week, Amis related an experience he had while speaking at London's Institute for Contemporary Arts. At one point, he asked members of the audience to raise their hands if they felt morally superior to the Taliban. Even taking into account the reluctance of a liberal audience to claim moral superiority about anything, it was surprising that only a third raised their hands.

We're talking about the Taliban here - mass executions, the oppression and enslavement of women, wholesale torture and the destruction of ancient art. A death cult no less and one which seems to have left no doubt about its intentions when more than 100 people were killed and hundreds more maimed by suicide bombers on Benazir Bhutto's return to Pakistan.

Amis's story suggests to me the sort of moral relativism that allowed Ken Livingstone to greet Egyptian-born cleric Yusuf al-Qaradawi, a homophobe and anti-semite who has expressed support for wife beating and suicide bombing. His views, its seems, were exactly the kind that were 'welcome in a city like London'.